Fungi produce a whole range of chemical compounds during normal metabolic processes which are generally classed as primary and secondary metabolites. The secondary metabolites consists of a large group of chemicals compounds (over 400 have been identified so far) with various effects on animals, bacteria and plants. The common mane of all of these chemicals is mycotoxins but depending of point of view they can be divided and classified in different ways.
Mycotoxins can be divided into multitude of groups based on the chemical structure of the core molecule forming the toxins. This classification would produce groups such as coumarins, lactones, alkaloids and many others. If the classification is based on the target organ in human or animal body the toxins can be grouped as neurotoxins, immunotoxins, hepatoxins, nephrotoxins and others. If mycotoxin effect on the cell rather the organ are considered then groups such as mutagens, carcinogens, allergen or teratogen can be identified. Mycologis would class mycotoxins based on the fungus which produces them such as Stachybotrys toxins, Fusarium toxins or Penicillium toxins and physician would divide them based on the type of illness they cause (aspergillosis, stachybotryotoxicosis, skin mycoses etc). Mycotoxins which are especially toxic to plants are called phytotoxins and those particularly toxic to bacteria are referred to as antibiotics. As you can see the definition and classification of a particular toxins depends on the point of view and therefore many toxins belong to many groups often causing confusion.
Mycotoxins are produce by fungi most likely due to the completion between different fungal species. They are as if, chemical weapons one fungus uses against another to gain competitive advantage. In macroscopic fungi (mushrooms) they can simply be produced to prevent mushroom to be eaten by animals before it had a change to release the spores. They also provide protection from other parasitic organisms or microscopic insect feeding on them. Mycotoxins can also help the fungus to gain entrance into normally healthy plant or animal body. Mycotoxins have many functions from which many are yet to be discovered.
Mycotoxins are contained in fungal bodies such as spores or hyphae but are also released into the substrate on which they grow. Because they are largely non-volatile organic compounds they are not released directly into the air. However exposure to mycotoxins can easily occur when inhaling fungal spores, fragment of fungal hyphae or airborne particles contaminated by toxins.
Mycotoxins are produced by great variety of fungi but the best known mycotoxins producers are Fusarium, Stachybotrys, Aspergillus and Penicillium moulds. Each mould species can produce its own array of toxins and many toxins can be produced by different moulds. Mycotoxins production depends greatly of the particular species, but also on a particular strain within one species. Environmental factors such as temperature, humidity and availability of nutrients (substrate) play an important role in toxin production. Ecological factors such as competition from other species can also influence toxin production.
Mycotoxins have been suggested as one of the major possible causes of the health problems observed in mouldy buildings. Probably the most important toxins from the health perspective are those produced by fusarium mould -fumonisins, but also trichothecenes ( nivalenol, T-2 toxin, deoxynivalenol) and alfatoxisn (B1, B2, M1, G1 anf G2). They cause a great variety of ill health effects in humans. Alfatoxins are considered to be carcinogenic and other mycotoxins have a range of other health effects including kidney damage, gastrointestinal disturbances, reproductive disorders or suppression of the immune system.
By Tomas Gabor
